Ever since I updated to Firefox 20 on my Mac (10.8.3) and the latest version of Flash Player, I've found any sites using flash videos to be extremely choppy if I switch tabs or pause and then play the video again. Not got the problem in Chrome or Safari so it leads me to believe its Firefox that is causing the issue and not Flash.

Anyone else noticed the issue? Is there a settings fix in about:config?

I have had this problem for a long time and have exhausted all possibilities. There seems to be a fundamental problem here. Why is it that people using all platforms are havine the same problem??? WIndows, Linux, MacOS does not seem to matter. I have tried all browsers on windows except opera. and all have had the same choppy problem for a couple of years even at the lowest resolutions. I used to be able to watch videos with no problems. I have more than 1GB ram free a 2GHZ processor. My hard drive is 80%free and defragmented (About 55GB free space) tried clearing cache, which should not matter anyway since browsers are supposed to auto limit the cache size. Tried disabling or enabling hardware acceleration, no change. Tried disabling protected mode for flash, no change. I think that flash is just a bloated crappy application that should be re-coded from scratch to be efficient. I do notice a massive increase in CPU usage during playback and the videos seem worse on embedded sites like those video links you can follow on the weather channel site. My system plays video files just fine, I can watch 720p avi or mkv files with no problem even tried a 1080p blue-ray rip file, even though the video was larger than my monitor can display what was visible was crystal clear and fluid with 60 frames per second playback. (I also do not have ANY anti-virus or anti spyware software on my computer at all. I do a "Right Now" kind of check periodically with trendmicro housecall) my video card cannot ahave it's drivers updated it is a radeon 9100, a "white box" card. ati does not support these cards at all and driver updates detect that it is not a real ati card and updates cancel out. but I could watch youtube videos with this system just fine 3 years ago. os=winxp sp3 I am about to give up.